Db schema cache dump and clear multi db

Adds support for multiple databases to `rails db:schema:cache:dump`
and `rails db:schema:cache:clear`.

Always add records to parent of nested transaction

When a record with transactional callbacks is saved, it's attached to
the current transaction so that the callbacks can be run when the
transaction is committed. Records can also be added manually with
`add_transaction_record`, even if they have no transactional callbacks.

When a nested transaction is committed, its records are transferred to
the parent transaction, as transactional callbacks should only be run
when the outermost transaction is committed (the "real" transaction).
However, this currently only happens when the record has transactional
callbacks, and not when added manually with `add_transaction_record`.

If a record is added to a nested transaction, we should always attach it
to the parent transaction when the nested transaction is committed,
regardless of whether it has any transactional callbacks.

[Eugene Kenny & Ryuta Kamizono]

Respond /rails/info/properties.json

Amend CVE note and security guide section wordings

Added json format, like this:

    {
      "Rails version": "6.0.0.alpha",
      "Ruby version": "2.5.1-p57 (x86_64-darwin17)",
      "RubyGems version": "2.7.6",
      "Rack version": "2.0.6",
      "JavaScript Runtime": "Node.js (V8)",
      "Middleware": ["Rack::Sendfile", "ActionDispatch::Static", "ActionDispatch::Executor", "ActiveSupport::Cache::Strategy::LocalCache::Middleware", "Rack::Runtime", "Rack::MethodOverride", "ActionDispatch::RequestId", "ActionDispatch::RemoteIp", "Sprockets::Rails::QuietAssets", "Rails::Rack::Logger", "ActionDispatch::ShowExceptions", "WebConsole::Middleware", "ActionDispatch::DebugExceptions", "ActionDispatch::Reloader", "ActionDispatch::Callbacks", "ActiveRecord::Migration::CheckPending", "ActionDispatch::Cookies", "ActionDispatch::Session::CookieStore", "ActionDispatch::Flash", "ActionDispatch::ContentSecurityPolicy::Middleware", "Rack::Head", "Rack::ConditionalGet", "Rack::ETag", "Rack::TempfileReaper"],
      "Application root": "/path/to/app",
      "Environment": "development",
      "Database adapter": "sqlite3",
      "Database schema version": 0
    }

Add `connect_src` example to content security policy initializer

Reword first sentence of dep management and CVE section of
security guide. Also, reword and move gemspec notes above deps.

[ci skip]

Add CVE note to security guide and gemspecs

[ci skip]

Fix inspect with non-primary key id attribute

The `read_attribute` method always returns the primary key when asked to
read the `id` attribute, even if the primary key isn't named `id`, and
even if another attribute named `id` exists.

For the `inspect`, `attribute_for_inspect` and `pretty_print` methods,
this behaviour is undesirable, as they're used to examine the internal
state of the record. By using `_read_attribute` instead, we'll get the
real value of the `id` attribute.

Fix DRb::DRbServerNotFound  errors in parallel tests

Fix typo [ci-skip]

Just a small typo fix for the recently merged #34257

If want to use `webpack-dev-server` with CSP enabled, need to specify
`connect-src`.
Related to: https://github.com/rails/webpacker/commit/cd7ecf4d48496341aecd81c0c2f69fe4e50a7cd4

This is a matter of `webpacker`. But since `webpacker` is now used by
default, to prevent user confusion, I think that better to include an
example of `connect-src.`

If add a package with `yarn`, it will have a newline after the last
dependency so let's match with that.

The `model_metadata` is only used if `model_class` is given.

If `model_class` is given, the `table_name` is always
`model_class.table_name`.

The `@connection` is no longer used since ee5ab222.

Originally the `@connection` was useless because it is only used in
`timestamp_column_names`, which is only used if `model_class` is given.

If `model_class` is given, the `@connection` is always
`model_class.connection`.

Convert ActionCable javascript to ES2015 modules with a modern build environment

We've replaced the sprockets `//= require` directives with ES2015
imports. As a result, the ActionCable javascript can now be compiled
with rollup (like ActiveStorage already is).

- Rename action_cable/index.js.erb -> action_cable/index.js

- Add rake task to generate a javascript module of the ActionCable::INTERNAL ruby hash

  This will allow us to get rid of ERB from the actioncable javascript,
  since it is only used to interpolate ActionCable::INTERNAL.to_json.

- Import INTERNAL directly in ActionCable Connection module

  This is necessary to remove a load-order dependency conflict in the
  rollup-compiled build. Using ActionCable.INTERNAL would result in a
  runtime error:
  ```
  TypeError: Cannot read property 'INTERNAL' of undefined
  ```
  because ActionCable.INTERNAL is not set before the Connection module
  is executed.

  All other ActionCable.* references are executed inside of the body of a
  function, so there is no load-order dependency there.

- Add eslint and eslint-plugin-import devDependencies to actioncable

  These will be used to add a linting setup to actioncable like the one
  in activestorage.

- Add .eslintrc to actioncable

  This lint configuration was copied from activestorage

- Add lint script to actioncable

  This is the same as the lint script in activestorage

- Add babel-core, babel-plugin-external-helpers, and babel-preset-env devDependencies to actioncable

  These will be used to add ES2015 transpilation support to actioncable
  like we have in activestorage.

- Add .babelrc to actioncable

  This configuration was copied from activestorage

- Enable loose mode in ActionCable's babel config

  This generates a smaller bundle when compiled

- Add rollup devDependencies to actioncable

  These will be used to add a modern build pipeline to actioncable like
  the one in activestorage.

- Add rollup config to actioncable

  This is essentially the same as the rollup config from activestorage

- Add prebuild and build scripts to actioncable package

  These scripts were copied from activestorage

- Invoke code generation task as part of actioncable's prebuild script

  This will guarantee that the action_cable/internal.js module is
  available at build time (which is important, because two other modules
  now depend on it).

- Update actioncable package to reference the rollup-compiled files

  Now that we have a fully functional rollup pipeline in actioncable, we
  can use the compiled output in our npm package.

- Remove build section from ActionCable blade config

  Now that rollup is responsible for building ActionCable, we can remove
  that responsibility from Blade.

- Remove assets:compile and assets:verify tasks from ActionCable

  Now that we've added a compiled ActionCable bundle to version control,
  we don't need to compile and verify it at publish-time.

  (We're following the pattern set in ActiveStorage.)

- Include compiled ActionCable javascript bundle in published gem

  This is necessary to maintain support for depending on the ActionCable
  javascript through the Sprockets asset pipeline.

- Add compiled ActionCable bundle to version control

  This mirrors what we do in ActiveStorage, and allows ActionCable to
  continue to be consumed via the sprockets-based asset pipeline when
  using a git source instead of a published version of the gem.

- Remove unnecessary Array.from usages from subscriptions.js

  These were all Arrays before, so Array.from is a no-op

- Remove unnecessary IIFEs from subscriptions.js

- Manually decaffeinate sample ActionCable code in comments

  Here the coffeescript -> ES2015 conversion was done by hand rather than
  using decaffeinate, because these code samples were simple enough.

- Refactor ActionCable.Subscription to avoid initClass

- Refactor ActionCable.Subscription to use ES2015 default parameters

- Refactor ActionCable.ConnectionMonitor to avoid initClass

- Refactor ActionCable.ConnectionMonitor to use shorter variations of null checks

- Remove unnecessary code created because of implicit returns in ConnectionMonitor

  This removes the `return` statements that were returning the value of
  console.log and those from private methods whose return value was not
  being used.

- Refactor ActionCable.Connection to avoid initClass

- Refactor Connection#isProtocolSupported and #isState

  This addresses these three decaffeinate cleanup suggestions:
  - DS101: Remove unnecessary use of Array.from
  - DS104: Avoid inline assignments
  - DS204: Change includes calls to have a more natural evaluation order

  It also removes the use of Array.prototype.includes, which means we
  don't have to worry about providing a polyfill or requiring that end
  users provide one.

- Refactor ActionCable.Connection to use ES2015 default parameters

- Refactor ActionCable.Connection to use shorter variations of null checks

- Remove return statements that return the value of console.log() in ActionCable.Connection

- Simplify complex destructure assignment in connection.js

  decaffeinate had inserted
  ```
  adjustedLength = Math.max(protocols.length, 1)
  ```
  to be safe, but we know that there has to always be at least one
  protocol, so we don't have to worry about protocols.length being 0 here.

- Refactor Connection#getState

  The decaffeinate translation of this method was not very clear, so we've
  rewritten it to be more natural.

- Simplify destructure assignment in connection.js

- Remove unnecessary use of Array.from from action_cable.js.erb

- Refactor ActionCable#createConsumer and #getConfig

  This addresses these two decaffeinate cleanup suggestions:
  - DS104: Avoid inline assignments
  - DS207: Consider shorter variations of null checks

- Remove unnecessary code created because of implicit returns in action_cable.js.erb

  This removes the `return` statements that were returning the value of
  console.log and those from methods that just set and unset the
  `debugging` flag.

- Remove decaffeinate suggestion about avoiding top-level this

  In this case, the top-level `this` is intentional, so it's okay to
  ignore this suggestion.

- Remove decaffeinate suggestions about removing unnecessary returns

  I did remove some of the return statements in previous commits, where
  it seemed appropriate. However, the rest of these should probably remain
  because the return values have been exposed through the public API. If
  we want to break that contract, we can do so, but I think it should be
  done deliberately as part of a breaking-API change (separate from this
  coffeescript -> ES2015 conversion)

- Remove unused `unsupportedProtocol` variable from connection.js

  Leaving this would cause eslint to fail

- Refactor Subscriptions methods to avoid `for` ... `of` syntax

  Babel transpiles `for` ... `of` syntax to use `Symbol.iterator`, which
  would require a polyfill in applications that support older browsers.

  The `for` ... `of` syntax was produced by running `decaffeinate`, but in
  these instances a simpler `map` should be sufficient and avoid any
  `Symbol` issues.

Using [decaffeinate], we have converted these files from coffeescript
syntax to ES2015 syntax. Decaffeinate is very conservative in the
conversion process to ensure exact coffeescript semantics are preserved.
Most of the time, it's safe to clean up the code, and decaffeinate has
left suggestions regarding potential cleanups we can take. I'll tackle
those cleanups separately.

After running decaffeinate, I ran:
```
eslint --fix app/javascript
```
using the eslint configuration from ActiveStorage to automatically
correct lint violations in the decaffeinated output. This removed 189
extra semicolons and changed one instance of single quotes to double
quotes.

Note: decaffeinate and eslint can't parse ERB syntax. So I worked around
that by temporarily quoting the ERB:
```diff
 @ActionCable =
-  INTERNAL: <%= ActionCable::INTERNAL.to_json %>
+  INTERNAL: "<%= ActionCable::INTERNAL.to_json %>"
   WebSocket: window.WebSocket
   logger: window.console
```
and then removing those quotes after running decaffeinate and eslint.

[decaffeinate]: https://github.com/decaffeinate/decaffeinate

- Rename action_cable/*.coffee -> *.js

- Move app/assets/javascripts/* -> app/javascript/*

- Rename action_cable.js.erb -> action_cable/index.js.erb

Renaming the extension to .js is in preparation for converting these
files from coffeescript to ES2015.

Moving the files to app/javascript and putting the entry point in
index.js.erb changes the structure of ActionCable's javascript to match
the structure of ActiveStorage's javascript.

(We are doing the file moving and renaming in a separate commit to
ensure that the git history of the files will be preserved - i.e. git
will track these as file renames rather than unrelated file
additions/deletions. In particular, git blame will still trace back to
the original authorship.)

Make ActiveSupport HashWithIndifferentAccess#to_options and alias for HashWithIndifferentAccess#symbolize_keys

Fixes #34359

Prior to 5.2.0 (2cad8d71), HashWithIndifferentAccess#to_options acted as
an alias to HashWithIndifferentAccess#symbolize_keys. Now, #to_options
returns an instance of HashWithIndifferentAccess while #symbolize_keys
returns and instance of Hash.

This pr makes it so HashWithIndifferentAccess#to_options acts as an
alias for HashWithIndifferentAccess#symbolize_keys once again.

Updating sample code on ActiveRecord#before_destroy callback [ci skip]

It was executing a delete_all method with wrong parameter

Make i18n locale setting docs use around_action

Changes `I18n.locale` assignment in docs to use `I18n.with_locale`
in `around_action` to ensure locale resetting after action processing.

[ci skip]

[Gannon McGibbon + Leonardo Tegon]

Caused at #34196.

Update authorization.rb

Restore HashWithIndifferentAccess support to
ActiveJob::Arguments.deserialize.

Fix example for database-specific locking clause

[ci skip]

Improve `enqueue_retry.active_job` message